| 摘要 |
PROBLEM TO BE SOLVED: To produce a good workability high strength cold rolled steel sheet excellent in formability in the weld zone and used for automotive outer board panels such as hoods, fenders and side panels. SOLUTION: This steel sheet is the one having components consisting of, by mass, 0.0040 to 0.01% C, <=0.05% Si, 0.1 to 1.0% Mn, 0.01 to 0.05% P, <=0.02% S, 0.01 to 0.1% sol.Al, <=0.004% N, 0.01 to 0.14% Nb, and the balance substantial Fe with inevitable impurities and also satisfying the inequalities I and II: the inequality I: (12×Nb*)/(93×C)>=1.2, where Nb*=Nb-(93/14)×N and the inequality II: TS(MPa)-4050×Ceq>=-0.75×TS(MPa)+380, where Ceq= C%+(1/50)Si%+(1/25)Mn%+(1/2)P%.
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